Applying Prentice's Rule Flashcards
7 cards from real ABO NOCE Basic Opticianry practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Applying Prentice's Rule flashcards as text
A patient's right eye requires 1.50Δ base in. The lens power is +3.00 D. In which direction and how far should the optical center be decentered?
Answer: 5 mm nasally
d = 1.50/3.00 = 0.5 cm = 5 mm; for a plus lens, decentering the OC nasally places the eye temporal to the OC, inducing base-in prism.
An optician finds 1.80Δ of induced prism in a -4.50 D lens. How far is the OC displaced from the MRP?
Answer: 4 mm
d = 1.80/4.50 = 0.4 cm = 4 mm.
Which of the following correctly states Prentice's Rule?
Answer: Δ = P × d (d in cm)
Prentice's Rule is Δ = P × d, where d must be in centimeters.
A +6.00 D lens is positioned so the patient looks through a point 3 mm above the optical center. What is the induced prism and base direction?
Answer: 1.80Δ base up
Δ = 6.00 × 0.3 = 1.80Δ; looking above the OC of a plus lens induces base-up prism because the base is toward the OC.
OD is +2.00 D decentered 4 mm temporally; OS is +2.00 D decentered 4 mm temporally. What is the total horizontal prismatic imbalance between the eyes?
Answer: 1.60Δ
Each eye: Δ = 2.00 × 0.4 = 0.80Δ; OD temporal decentration = base out OD; OS temporal decentration = base out OS; both base out means they compound, creating 1.60Δ total imbalance for vergence.
When using Prentice's Rule in a trifocal, which power is used for a point within the intermediate segment?
Answer: Distance power plus intermediate add power
The effective power at any segment zone equals the distance power combined with that segment's add power.
A -1.50 D lens is decentered 5 mm temporally for the left eye. What prismatic effect does this create?
Answer: 0.75Δ base in
Δ = 1.50 × 0.5 = 0.75Δ; for a minus lens in the left eye decentered temporally, the base points toward the decentration = temporal = base in for the left eye.